The 2020 Olympic and Paralympic host city will be decided this weekend in Buenos Aires.
International Olympic Committee (IOC) members will take part in a secret ballot to decide between contenders Tokyo, Madrid and Istanbul.
The announcement of the successful city will take place at 2100 BST with bookies making the Japanese capital the slight favourites.
The IOC will also vote on one of squash, baseball/softball or wrestling to be added to the 2020 programme.
Istanbul has been beset by problems after political protests in June caused unrest in the city, as well as a doping scandal which implicated over 30 track and field athletes in Turkey.
Tokyo is attempting to allay fears over the Fukushima nuclear power plant which continues to leak radioactive water into the Pacific.
The Madrid bid meanwhile has continually been affected by Spain's precarious economic situation and high unemployment levels.
Mike Lee, the head of Vero Communications who worked on the successful Olympic bids for London 2012, Rio de Janeiro 2016 and Pyeongchang 2018 (Winter Olympics), cannot pick a winner.
"All the bid teams have been forced onto the defensive for a large part of this campaign because of a range of issues," he said.
"It does still feel that there is a lot to play for, and the final presentations and last two days of lobbying could be very important."
The Tuesday following the announcement will see IOC president Jacques Rogge step down after 12 years in the post.
A secret ballot will then take place to decide his replacement form a group of six candidates.
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